Was this said prior to the formulation of modern QFT? I imagine Tesla would agree that QFT is the thing to be done to add waviness to the particular questions we humans like to ask, although he didn't exactly believe in the concept of electron, maybe he would see its formulation in QFT and say yes?

I think Tesla would still object to seeing quantum phenomena through such a classical lens. It is very much ”not seeing the forest for the trees”.

In fact, Tesla might even object to the usage of the word ”quantum”, since it implies that same top-down view. Tesla would start from the field(s) and let whatever phenomena emerge from that, quantized or not.

Tesla may have been a capable engineer in his early years (before turning into a crackpot and/or fraud). However, his understanding of modern physics appears to have been extremely poor. He certainly has not contributed anything significant to the field.